Non-24-hour Sleep Wake Disorder Facts & Prevalence

This content was created by the National Sleep Foundation

Non-24-Hour Sleep Wake Disorder (Non-24) is a disorder that affects the normal 24-hour synchronization of circadian rhythms. One subtype designation according to the International Classification of Sleep Disorders is Circadian Rhythm Sleep Disorder - Free Running Type. It has also been called Hypernychthemeral Syndrome.